This invention relates to a microencapsulated family of phytotoxic fungicides. More particularly, it relates to products which are phytotoxic fungicidal benzothiazole related compounds microencapsulated within walls of crosslinked polyamide, crosslinked polyurea or crosslinked polyamide-polyurea to provide an effective agent for direct foliar application to control fungal diseases on crops.
The microencapsulation of organophosphate insecticides has been previously used to upgrade characteristics that are lacking in these materials. Encasing the pesticide in an appropriate polymer shell increases residual by protecting it from substrate adsorption, vaporization and the general environment until such time as the target species contacts the capsule or else is exposed to vapors of active ingredient emanating from the capsule. Increased efficiency is obtained primarily by the concentrating effect of microencapsulation whereby the pesticide exists on the substrate in numerous point sources with much area between the capsules untreated. For example, when using capsules having an average size of 30 microns (.mu.m) at the treatment level of 1 lb/acre, calculations show that greater than 99% of the area is not covered by capsules.
Because of the absence of microcapsules over such a large proportion of the area of treatment, it was reasoned by those skilled in the art.sup.1, that the microencapsulation of fungicides would result in effects counter to those desired since proper usage of fungicides demands a maximum coverage of the treated area. In fact, there are presently no instances of commercial products which are microencapsulated fungicides. FNT .sup.1 R. C. Koestler, "A Theory of Mechanism of Action of Encapsulated Herbicides and Insecticides", in 3rd International Controlled Release Pesticide Symposium, Sept. 1976